1. Field of the Invention
This invention relates to an apparatus for drying a ceramic green honeycomb body.
2. Description of the Prior Art
A known procedure for forming a ceramic green honeycomb body by extruding the ceramic material body through a die. The thus formed ceramic green honeycomb body includes a plurality of parallel through holes separated from each other by partition walls of substantially uniform thickness. For instance, U.S. Pat. No. 3,824,196 discloses a die to be set on an extruder for extruding such ceramic green honeycomb bodies from a ceramic material body, which die has a configuration corresponding to the cross-sectional configuration of the ceramic green honeycomb body. In reference to the method of drying the thus extruded green honeycomb body, for instance, U.S. Pat. No. 3,954,672 discloses a dielectric drying process which applies high-frequency energy from a pair of facing electrodes to the ceramic green honeycomb body, whereby the ceramic green honeycomb body is dried by the heat generated therein through the dipole-dipole interaction in water due to the high-frequency energy.
However, the dielectric drying of the ceramic green honeycomb body according to the prior art has a shortcoming in that the density of electric lines of force is not uniform in the ceramic green honeycomb body and localized high-moisture zones are formed, and such high-moisture zones are found to be hard to eliminate either by elongating the duration of the dielectric heating or by increasing the high-frequency energy. When the ceramic green honeycomb body is placed on a non-metallic support board so that the through holes thereof are kept perpendicular to the support board during the dielectric heating, the above-mentioned high-moisture zones are formed in the proximities of the upper and lower ends of the green honeycomb body, as shown by the curve a of FIG. 4. After the ceramic green honeycomb body is dried, if such high-moisture zones are severed off from the thus dried green honeycomb body by using a grindstone, the through holes at the severed surface are apt to be plugged. The presence of the localized high-moisture zones tends to cause uneven shrinkage and cracks in the honeycomb body during firing.
To mitigate the above-mentioned difficulty in the severing of the high-moisture zones from the dried body, the severing may be effected after the firing. However, since the fired good is harder than the dried body, the severing after the firing has shortcomings in that much time and energy are necessary to complete the severing and that the grindstone for the severing is worn out quickly thus increasing the cost of the severing work.